Carbon-carbon composites which have been densified with pitches and used as friction materials typically exhibit higher wear rates compared with carbon-carbon composite that have been densified by CVI/CVD processing. The higher wear rate of C-C composites comprised of pitch matrices results in the friction materials having to be replaced on a more frequent basis, which has a negative impact on operating costs for the end user.
A series of patent publications by Huang et al. are direct to the manufacture of carbon composites wherein carbon preforms are subjected to one or two infiltration cycles using pitch or other carbonaceous materials to fill voids in the composite. See US 2005/0274581; US 2004/0105969; US 2004/0155382; US 2004/0017019; and U.S. Pat. No. 6,699,427.
Murdie et al. disclose the formation of carbon composite articles. U.S. Pat. No. 6,323,160. The Murdie disclosure deals with densification of carbon preforms by various known techniques, including CVD, CVI, and pitch impregnation followed by carbonization. Murdie et al. teach that combinations of these techniques are often used to make a final product. See column 10, lines 34 and following.
U.S. Pat. Nos. 5,061,414 and 5,217,657 (Engle) disclose a method of making carbon-carbon composites from a pitch-impregnated preform followed by carbonization, with further pitch-impregnation steps with heat treatments between each impregnation, followed by CVD.